Modeling and Performance Analysis of PID …

1 International Journal of Scientific and Research Publications, Volume 3, Issue 4, April 2013 1 ISSN 2250-3153 Modeling and Performance Analysis of PID controlled BLDC Motor and Different Schemes of PWM controlled BLDC Motor Vinod KR Singh Patel*, ** * DEPARTMENT OF ELECTRICAL ENGINEERING, ENGINEERING COLLEGE, GORAKHPUR ( ), RESEARCH SCHOLAR (ELECTRICAL ENGINEERING, ENGINEERING COLLEGE) ** ASSOCIATE PROF (ELECTRONICS ENGINEERING, ENGINEERING COLLEGE) Abstract- Brushless dc (BLDC) motor drives are continually gaining popularity in motion control applications. Therefore, it is necessary to have a low cost, but effective BLDC motor speed/torque regulator. They are used in Residential and commercial appliances such as refrigerators and air conditioning systems with conventional motor drive technology. A Brushless DC (BLDC) drives are known for higher efficiency and lower maintenance. This paper presents a Modeling and Performance Analysis of PID controlled BLDC motor and different schemes of PWM controlled BLDC motor.

2 This paper presents PID model of brushless dc (BLDC) motor with the use of MATLAB/ SIMULINK. The operational parameters of specific BLDC motor were modeled using the tuning methods which are used to develop subsequent simulations. Index Terms- Brushless DC motor (BLDCM), Digital pulse width modulation (DPWM) PID controllers I. INTRODUCTION he use of the general type dc motor has its long history. It has been used in the industries for many years now. They provide simple means and precise way of control [1]. In addition, they have high efficiency and have a high starting torque versus falling speed characteristics which helps high starting torque and helps to prevent sudden load rise [2]. the brushless direct current (BLDC) motor are gaining grounds in the industries ,especially in the areas of appliances production ,aeronautics ,medicine, consumer and industrial automations and so on.

3 The BLDC are typically permanent synchronous motor, they are well driven by dc voltage. They have a commutation that is done mainly by electronics application. Some of the man y advantages of a brushless dc motor over the conventional brushed dc motors are highlighted below [3]: 1. Better speed versus torque characteristics 2. High dynamic response 3. High efficiency 4. Long operating life 5. High speed ranges 6. Low maintenance (in terms of brushes cleaning; which is peculiar to the brushed dc motor). The PID controller is applied in various fields of engineering, and it is also a very important tool in telecommunication system. If there is a system and stability is desired, then PID could be very useful. In practice, the design of the BLDCM drive involves a complex process such as Modeling , control scheme selection, simulation and parameters tuning etc.

4 An expert knowledge of the system is required for tuning the controller parameters of servo system to get the optimal Performance . Recently, various modern control solutions are proposed for the speed control design of BLDC motor [4]. However, Conventional PID controller algorithm is simple, stable, easy adjustment and high reliability, Conventional speed control system used in conventional PID control [5]. But, in fact, most industrial processes with different degrees of nonlinear, parameter variability and uncertainty of mathematical model of the system. Tuning PID control parameters is very difficult, poor robustness, therefore, it's difficult to achieve the optimal state under field conditions in the actual pwm control method is a better method of controlling, to the complex and unclear model systems, it can give simple and effective control. Proportional-integral (PI) control with hysteresis or pulse width modulation (PWM) switching is the most widely used speed control technique for BLDC motors with trapezoidal back EMF.

5 It can be easily implemented on analog or digital components because it is well understood, simple, and in practice for a fairly long period of time. To enhance the Performance or to reduce the cost has been focus of development work for a long time. Cost and implementation complexity are often the most important factors for design trade-offs between techniques, implementation, and strategy of motor control hardware. The aim of this paper is that it shows the dynamics response of speed with design the PID controller to control a speed of motor for keeping the motor speed to be constant when the load varies. II. BRUSHLESS DC MOTOR AND MODEL CONCEPT One of the major differences between the DC motor and the BLDC is implied from the name. the conventional dc motor has brushes that are attached to its stator while the brushes DC motor does not. Also, unlike the normal DC motor, the commutation of the BLDC could be done by electronic control [3].

6 Under the BLDC motor, the stator windings are energized in sequence for the motor to rotate. More also, there is no physical contact whatsoever between the stator and the rotor. Another vital part of the BLDC is the hall sensor(s); these hall sensors are systematically attached to the rotor and they are used as major T International Journal of Scientific and Research Publications, Volume 3, Issue 4, April 2013 2 ISSN 2250-3153 sensing device by the Hall Effect sensor embedded into the stator [3]. This works based on the principal of Hall Effect. The BLDC motor operates in many modes (phases), but the most common is the 3-phase. The 3- phase has better efficiency and gives quite low torque. Though, it has some cost implications, the 3-phase has a very good precision in control [6]. And this is needful in terms of the stator current. Mathematical model of a typical BLDC motor Typically, the mathematical model of a Brushless DC motor is not totally different from the conventional DC motor.

7 The major thing addition is the phase involved which affects the overall result of the BLDC model. The phase peculiarly affects the resistive and the inductive of the BLDC arrangement. DC MotorInertia Load, JTorqueAngular rateViscous frictionLRLRLRRL-LKeL-L Brushless DC motor schematic diagram For the mechanical time constant (with symmetrical arrangement), equation becomes: ( ) the electrical (time constant), ( ) Therefore, since there is a symmetrical arrangement and a there phase, the mechanical (known) and electrical become: Mechanical constant, ( ) Electrical constant, ( ) Where, Therefore, the equation for the BLDC is ( ) III. MAXON BLDC MOTOR Maxon EC 45 flat 45 mm, brushless DC motor The BLDC motor provided for this paper is the EC 45 flat 45 mm, brushless, 30 Watt from Maxon motors [7].

8 The order number of the motor is 200142. The parameters used in the Modeling are extracted from the datasheet of this motor with corresponding relevant parameters used. Find below in Table the major extracted parameters used for the Modeling task. Maxon Motor Data Unit Value Values at nominal voltage 1 Nominal Voltage V 2 No load Speed rpm 4370 3 No load Current mA 151 4 Nominal Speed rpm 2860 5 Nominal Torque (max. continuous torque) mNm 6 Nominal Current (max. continuous current) A 7 Stall Torque mNm 255 8 Starting Current A 9 Maximum Efficiency % 77 Characteristics 10 Terminal Resistance phase to phase International Journal of Scientific and Research Publications, Volume 3, Issue 4, April 2013 3 ISSN 2250-3153 BLDC MOTOR PARAMETERS USED [7] IV. BLDC MAXON MOTOR MATHEMATICAL MODEL The mathematical model of the BLDC motor is modelled on the parameters from table given above.

9 ( ) So the values for need to calculated to obtain the motor model .. ( ) But is a function of R, J, and Then Therefore, the G(s) becomes: .. ( ) The G(s) derived above in the equation is the open loop transfer function of the Brushless DC maxon motor using all necessarily sufficient parameters available. Open Loop Analysis using MATLAB m- file With the aid of the BLDC motor parameters provided, the open loop Analysis is done by considering the stability factors and making the necessary plots for this Analysis . Some of the plots include the step response, root locus, nyquist diagram, and bode plot diagram. Open loop step response diagram 11 Terminal Inductance phase to phase mH 12 Torque Constant mNm/A 13 Speed Constant rpm/V 14 Speed/Torque Gradient rpm/mNm 15 Mechanical time constant ms 16 Rotor Inertia gcm2 17 Number of phase 3 International Journal of Scientific and Research Publications, Volume 3, Issue 4, April 2013 4 ISSN 2250-3153 Open loop step root locus diagram Figure.

10 4. Open Loop step Nyquist diagram International Journal of Scientific and Research Publications, Volume 3, Issue 4, April 2013 5 ISSN 2250-3153 Figure. 5. Open Loop Step Bode Plot diagram V. PID DESIGN CONCEPT The Proportional-Integral-Derivative (PID) controller is about the most common and useful algorithm in control systems engineering [8]. In most cases, feedback loops are controlled using the PID algorithm. The main reason why feedback is very important in systems is to be able to attain a set-point irrespective of disturbances or any variation in characteristics of any form. Consider the characteristics parameters proportional (P), integral (I), and derivative (D) controls, as applied to the diagram below in figure 2, the system, S is to be controlled using the controller, C; where controller, C efficiency depends on the P, I and D parameters [7]. CONTROLLERSYSTEMRY+-eu Figure.